Transfer switch for tap changing regulating transformers with improved contact structure

ABSTRACT

A transfer switch structure for tap-changing regulating transformers includes a cylindrical contact support for fixed contacts, cooperating movable contacts arranged inside the support and a liquid containing tank for housing said contact support. The tank is provided with terminals. A novel contact structure including spring-biased superimposed contact fingers forming an X-like pattern is provided for transferring current from the movable current-carrying contacts to the terminals of the transfer switch.

[ June 12, 1973 United States Patent 1 Wittenzellner et a1.

2,577,225 12/1951 200/11 B 3,238,318 3/1966 Bleibtreu et a1. 200/8 A X3,458,670 7/1969 Wittenzellner............ 200/166 BE X TRANSFER SWITCHFOR TAP-CHANGING REGULATING TRANSFORMERS WITH IMPROVED CONTACT STRUCTUREInventors: Georg Wittenzellner,

FOREIGN PATENTS OR APPLICATIONS 1,230,903 12/1966 Germany Oberhinkhofen;Hans Stark, Regensburg, both of Germany Primary Examiner-J. R. ScottAtt0rneyErwin Salzer n e, we

i e a Rem hun a b MGR 22 Filed: Jan. 25, 1972 ABSTRACT Appl. No.:220,668

A transfer switch structure for tap-changing regulating transformersincludes a cylindrical contact support for fixed contacts, cooperatingmovable contacts arranged [30] Foreign Application Priority Data Feb. 2,1971 Germany................... P 21 04 766.5

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movable current-carrying contacts to the terminals of the transferswitch.

[56] References Cited UNITED STATES PATENTS 3,238,320 3/1966 Bleibtreu200/8 A X 5 Claims, 3 Drawing Figures PAIENR JUN 1 2197s sum 1 or 2 1TRANSFER SWITCH FOR TAP-CHANGING REGULATING TRANSFORMERS WITH IMPROVEDCONTACT STRUCTURE BACKGROUND OF THE INVENTION This invention refers totransfer switches for tapchanging regulating transformers and moreparticularly to transfer switches known as Jansen-type transferswitches.

The principal object of the invention is to provide transfer switches ofthe above description with currentcarrying contact means which do notinvolve braids, or similar flexible conductors.

US. Pat. No. 3,238,318 to A.Bleibtreu et al., Mar. 1, 1966 for CONTACTBRIDGES FOR RADIAL CON- TACTS WITH FULCRUM AND RESILIENT SPRINGSTRUCTURE discloses a Jansen-type transfer switch havingcurrent-carrying contacts of which the present invention is anoutgrowth, and a considerable improvement.

The structure disclosed in the above patent includes a substantiallycylindrical contact support supporting a plurality of fixed contactsarranged in a circular pattern. Said plurality of fixed contactsincludes a pair of fixed current-carrying contacts. A plurality ofmovable contacts is arranged inside of the aforementioned contactsupport. Each of said plurality of movable contacts is provided withoperating means to effect selective en gagement and disengagement of oneof said plurality of fixed contacts by one of said plurality of movablecontacts in a predetermined sequence. The aforementioned plurality ofmovable contacts includes a pair of movable current-carrying contactseach arranged to cooperate with one of said pair of fixedcurrentcarrying contacts. The transfer switch further includes a tankadapted to house said contact support and to be filled with a liquidmedium, such as oil, for immersing said plurality of fixed contacts andsaid plurality of movable contacts therein. The tank for housing thecontact support and the entire transfer switch mechanism is providedwith and supports a pair of terminals each adapted to be conductivelyconnected to one of said fixed current-carrying contacts. Each of saidpair of terminals has a contact surface situated on the inside of theabove referred-to tank.

The above structure has been clearly illustrated in FIG. 2 of theaforementioned US. Pat. No. 3,238,318 wherein reference numeral 2 hasbeen applied to indicate the cylindrical contact support, numeral 23 toindicate the fixed contacts supported by support 2, numeral 22 toindicate the movable contacts cooperating with fixed contacts 23, andnumeral 3 to indicate terminals on a tank of insulating materialarranged in coaxial relation to contact support 2 and housing thelatter.

The external terminals on the tank have contact surfaces situated insideof the tank which are normally engaged under pressure by the fixedcurrent-carrying contacts. The aforementioned contact surfaces of theterminals and the portions of the fixed current-carrying contacts whichare normally in engagement with them operate as disconnect switch means.These disconnect switch means make it possible to assemble the transferswitch by a mere insertion of the contact support into the tank, and todisassemble the transfer switch by a mere withdrawal of the contactsupport from the tank.

In order to allow the terminals and the fixed currentcarrying contactsto cooperate in the above disconnectswitch-like fashion the fixedcontacts must be subject to a strong spring bias and given a smallfreedom of substantially radial motion relative to the cylindricalsupport for the fixed contacts. This requirement of a small freedom ofmotion calls for the provision of braids or similar flexible contactmeans. The design of braids, or like flexible current-carrying means, isdifficult, particularly if large current intensities are involved,because the presence of the flexible currentcarrying means must notimpair the freedom of motion of the spring-biased contact surfaces.Besides, the performance of braids and like flexible current-carryingmeans is often rather unsatisfactory.

It is one object of this invention to substitute for braids, and likeflexible current-carrying means, contact structures not subject to thedrawbacks and limitations of braids and like conductors of electricity.

SUMMARY OF THE INVENTION The present invention consists of a novelfinger contact structure for carrying current from the movablecurrent-carrying contacts of a transfer switch to the terminals thereof.The finger contacts include a pair of spring-biased superimposed contactfingers arranged cross-wise to form an X-like pattern. Each of said pairof contact fingers has a radially inner contact surface arranged to beengaged by one of a pair of movable current-carrying contacts and eachof said pair of contact fingers further has a radially outer contactsurface arranged to engage a radially inner contact surface of one of apair of terminals supported by the tank of the transfer switch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat diagrammatictransverse section of a three-phase transfer switch embodying theinvention and shows the constituent parts of one of the three phasesonly, the constituent parts of the other two phases of the transferswitch being broken away;

FIG. 2 is a side elevation of the current-carrying finger contactstructure which forms the essential element of the present invention andFIG. 2 further shows in cross-section the way in which theaforementioned finger contact structure is supported and positioned; and

FlG.3 is a front view of the structure of FIG.2 seen from the left tothe right of P162, or in radially inward direction of FIG.1

DESCRIPTION OF PREFERRED EMBODIMENT In the drawings reference character2 has been applied to indicate a substantially cylindricalcontactsupporting structure of electric insulating material. Structure 2supports a plurality of fixed contacts 5,6 arranged in a circularpattern. Contacts 5 are arcing contacts and contacts 6 arecurrent-carrying contacts within the meaning normally attributed tothese terms. A plurality of movable contacts is arranged inside contactsupport 2. Each of these movable contacts is provided with operatingmeans 3 to effect selective engagement and disengagement of one of saidplurality of fixed contacts by one of said plurality of movablecontacts. The movable contacts include the movable arcing contacts 4cooperating with the fixed arcing contacts 5 and the movablecurrent-carrying contacts 6 cooperating with the fixed current-carryingcontacts 6. The contact-operating means are formed by linkages driven byshaft 31 arranged in coaxial relation to contact support 2.

The structure shown in FIG. 1 may be designed and operate along thelines disclosed in considerable detail in U.S. Pat. No. 3,218,400 to A.Bleibtreu,Nov. 16,1965 for TRANSFER SWITCH FOR TAP- CHANGING REGULATINGTRANSFORMERS HAVING SQUIRREL-CAGE-SHAPED SUPPORT FOR THE FIXED CONTACTSTHEREOF; the aforementioned US. Pat. No. 3,238,318 to A.Bleibtreu etal., March 1,1966 for CONTACT BRIDGES FOR RA- DIAL CONTACTS WITH FULCRUMAND RESIL- IENT SPRING STRUCTURE; or U.S. Pat. No. 3,458,670 toG.Wittenzellner, July 29,1969 for TAP CHANGER CONTACT BRIDGE WITHSPRING- BIASED LOST MOTION CONNECTION. Reference may be had to thesepatents in regard to the details of the structure shown in FIG.1. Itshould be understood that movable contacts 4 may be formed by movablecontact bridges each adapted to conductively interconnect, or toseparate, a pair of fixed contacts taking the place of the fixedcontacts 5 of FIG.1. This modification of the structure of FIG.1 hasbeen shown and described in detail in the above referred-to prior artpatents.

In FIG.1 reference character 1 has been applied to indicate a tank ofelectric insulating material adapted to house, and housing, contactsupport 2, the fixed contacts 5,6 on support 2, their cooperatingmovable contacts 4,6 and the operating means 3,31 of the latter.Insulating tank 1 is arranged in coaxial relation to the cylindricalcontact support 2, and the former is adapted to be filled with a fluidmedium, e.g. oil, for immersing the fixed contacts 5,6 and the movablecontacts 4,6 in the fluid medium. The latter has not been shown in thedrawings. The tank 1 supports a pair of angularly displaced terminals ofwhich each is adapted by means in the nature of a disconnect switch tobe conductively connected to one of the movable and the fixedcurrentcarrying contacts 6',6. To this end each of the terminals 10 hasa contact surface situated inside of tank 1 the function of whichcontact surface will be explained below more in detail.

The aforementioned fixed pairs of current-carrying contacts 6 are shownin FlG.2 less diagrammatically, more in detail and on a larger scalethan in FIG.1. Each pair of fixed current-carrying contacts includes apair of spring-biased superimposed contact fingers 8,9 arrangedcrosswise to form an X-like pattern. Each of contact fingers 8,9 has aradially inner contact surface 81 and 91, respectively, formed by abulge-like projection. Each of contact fingers 8,9 further has aradially outer contact surface 82, and 92, respectively, each formed bya bulge-like projection. The radially inner contact surfaces 81,91 ofcontact fingers 8,9 are arranged to be engaged selectively by one of themovable current-carrying contacts 6. This results in a radially outwardmovement of contact fingers 8,9 against the bias of helical compressionsprings 11,11. As a result of this movement of contact fingers 8,9radially outer contact surfaces 82,92 engage under pressure the contactsurfaces of terminals 10. Thus the contact fingers 8,9 which are formedby planar stampings arranged in parallel planes establish current pathsof high conductivity from one of movable current-carrying contacts 6 toone of the terminals 10.

As mentioned above, FIG.1 shows a section of a portion of a tripolartransfer switch intended for threephase circuits. The same, or a similararrangement as shown in FIG.1 may be used for single-phase circuits. Inthe case of three-phase circuits one sector of about of cylindricalcontact support 2 supports the fixed contacts pertaining to one of threephases as shown more in detail in the prior art patents which have beenidentified above.

It will be apparent from F IG.2 that each of the helical compressionsprings 11 is interposed between the radially inner contact surface81,91 of one of the pair of contact fingers 8,9 and the radially outercontact surface 92,82 of the other of the pair of contact fingers 9,8.

The cylindrical contact support 2 is provided with a pair of cutouts 2'.Each of said pair of cut-outs is arranged at one of the two points wherethe contact fingers 7,8 are arranged to be engaged by the movablecurrent-carrying contacts 6'. A contact finger support 12 of electricinsulating material is inserted into each of the cut-outs 2' and affixedto the cylindrical contact support 2. This is preferably achieved bymeans of bolts or studs to which reference numeral 14 has been applied.Each of the contact fingers 8,9 is provided adjacent the axially outerend thereof with an abutmentforming surface cooperating with one of fourabutment studs 13 in order to limit the displacement of contact fingers8,9 relative to support 12 under the action of biasing springs 11.Springs 11 tend to cause engagement under pressure of abutment means orabutment pins 13 and finger contacts 8,9.

Contact finger support 12 is provided with a relatively large centralaperture or passageway 12 and with a pair of additional relatively smallapertures or passageways 12". passageways l2 and 12" extend from oneside to the other side of the contact finger support 12 in each of thecut-outs 2 in the cylindrical contact support 2. Each of contact finger8,9 projects substantially transversely through the central passageway12. Each of the compression springs 11 is arranged in one of theadditional passageways 12" of contact finger support 12 in each ofcut-outs 2. The abutment pins 13 are arranged at substantially rightangles to the two parallel planes defined by contact fingers 8,9.

A single pair of contact fingers 8,9 is capable of carrying butrelatively small currents from movable main contacts 6' to the terminals11) on tank 1. Where large currents are involved, the arrangement offingers 8,9 shown in FlG.2 may be multiplied as shown in FlG.3 In FIG.3reference numeral 12 has been applied to a contact finger support havingsubstantially the same geometrical configuration as the contact fingersupport of P162, except for the fact that the depth of the centralpassageway 12' is increased to allow passage of a stack composed ofsubstantially flat contact fingers 8,9 arranged in parallel planes. Theaforementioned stack of contact fingers 8,9 includes a plurality ofpairs of finger contacts 8,9. Each of said pair of contact fingers 8,9includes a pair of spring biased superimposed contact fingers arrangedcrosswise to form an X-like pattern as shown in FIG.2 and described indetail in connection with that figure. In other words, the structure ofFIGS. 2 and 3 differ only inasmuch as the former shows but one singlepair of contact fingers 8,9 which are arranged crosswise, and the lattershows three such pairs of crosswise arranged contact fingers.

We claim as our invention:

1. A transfer switch structure for tap-changing regua pair of abutmentsurfaces each cooperating with abutment means on said contact fingersupport to limit the displacement of said pair of contact fingers underthe action of said pair of helical comlating transformers including 5pression springs; and wherein a. asubstantially cylindrical contactsupport supportd, id i f heli al compression springs is suping aplurality of fixed Contacts arranged in a Circu' ported by said contactfinger support and tends to lar pattern, said plurality of fixedcontacts includcause engagement under pressure f id i f ing a P of fixedcurrent-carrying Contacts; abutment surfaces of each of said pair ofcontact a plurality of movable contacts arranged inside 10 fingers withsaid abutment means on said contact said contact support, each of saidplurality of movfinger Support able contacts being Provided withoperating means 4. A transfer switch structure as specified in claim 3to effect selective engagement and disengagement wherein of one of sfildplurality of fixed contacts by one of a. said contact finger support ineach of said pair of said plurality of movable contacts in apredetercupoms of Said cylindrical Contact support is mined sequence,said plurality of movable coma bolted to said cylindrical contactsupport and pro-, mcludmg a pan of movable curremfcartymg vided with arelatively large central passageway malts each arranged to COQPemte withone of said and with a pair of additional relatively small paspalr offixed cumm'carryllg contacts; sageways each arranged to opposite sidesof said c. a tank adapted to house said contact support and centralpassageway Said central passageway and to be filled with a fluid mediumfor immersing said f dditional assa ewa s extendin from plurality offixed contacts and said plurality of Sal P 0 a g y g one side to theother side of said contact finger supmovable contacts in said fluidmedium; port in each of said pair of cut-outs of said Cylllldl'ld.alpairdotf ttzrmlnalsi sutpprirted by satin:i tank eaclti cal Contact pps ai d t zir o f fix ed iiriieiiifai Jii g ftfnfac i=1: 3f each of Saidpair of Contact fingers projects Substantially transversely through saidcentral passagesald pair of terminals having a contact surface sltuatedon the inside of Said tank; and way of said contact finger support ineach of said e. each of said pair of fixed current-carrying contacts ofcut-Puts sald i coritact p including a pair of springbiased Superimposedeach of said pair of helical compression springs is contact fingersarranged crosswise to form an X- arranged one of sal d pan of Fpassagfe' like pattern, each of Said pair of Contact fingers ways ofsaid contactfmger support 1n each of said having a radially innercontact surface arranged to of 531d y al ontact support; and be engagedby one of said pair of movable currentwh erem carrying contacts and eachof said pair of Contact d. said abutment means on said contact fingersupfingers further having a radially outer contact surface arranged toengage said contact surface of one of said pair of terminals uponengagement of said radially inner contact surface thereof by one of saidport in each of said cut-outs of said cylindrical contact support isformed by four pins arranged substantially at right angles to the planesdefined by said pair of contact fingers.

5. A transfer switch structure as specified in claim 1 wherein a. saidcylindrical contact support is provided with a pair of movablecontact-carrying contacts. 40 2. A transfer switch structure asspecified in claim 1 including a pair of helical compression springs forbiasing said pair of contact fingers, each of said pair of compressionsprings being interposed between said rapair of cut-outs;

b. a contact finger support is inserted into each of dially innercontact surface of one of said pair of con- Said P of Cut-Outs andaffixed to Said cylindrical tact fingers and said radially outer surfaceof the other Contact pp and wherein of said pair of contact fingers.said contact finger support in each of said pair cut- 3. A transferswitch structure as specified in claim 2 u Of Said cylindrical contactsupport supports a wherein stack composed of substantially flat fingercontacts a. said cylindrical contact support is provided with a arrangedin parallel planes and including a plurality pair of cutouts; of pairsof finger contacts, each of said pairs of finb. a contact finger supportis inserted into each of ger contacts comprising a pair of spring-biasedsusaid pair of cut-outs and affixed to said cylindrical perimposedcontact fingers arranged crosswise to contact support; form an X-likepattern. c. each of said pair of contact fingers is provided with

1. A transfer switch structure for tap-changing regulating transformersincluding a. a substantially cylindrical contact support supporting aplurality of fixed contacts arranged in a circular pattern, saidplurality of fixed contacts including a pair of fixed current-carryingcontacts; b. a plurality of movable contacts arranged inside saidcontact support, each of said plurality of movable contacts beingprovided with operating means to effect selective engagement anddisengagement of one of said plurality of fixed contacts by one of saidplurality of movable contacts in a predetermined sequence, saidplurality of movable contacts including a pair of movablecurrent-carrying contacts each arranged to cooperate with one of saidpair of fixed current-carrying contacts; c. a tank adapted to house saidcontact support and to be filled with a fluid medium for immersing saidplurality of fixed contacts and said plurality of movable contacts insaid fluid medium; d. a pair of terminals supported by said tank eachadapted to be conductively connected to one of said pair of fixedcurrentcarrying contacts, each of said pair of terminals having acontact surface situated on the inside of Said tank; and e. each of saidpair of fixed current-carrying contacts including a pair ofspring-biased superimposed contact fingers arranged crosswise to form anX-like pattern, each of said pair of contact fingers having a radiallyinner contact surface arranged to be engaged by one of said pair ofmovable currentcarrying contacts and each of said pair of contactfingers further having a radially outer contact surface arranged toengage said contact surface of one of said pair of terminals uponengagement of said radially inner contact surface thereof by one of saidpair of movable contact-carrying contacts.
 2. A transfer switchstructure as specified in claim 1 including a pair of helicalcompression springs for biasing said pair of contact fingers, each ofsaid pair of compression springs being interposed between said radiallyinner contact surface of one of said pair of contact fingers and saidradially outer surface of the other of said pair of contact fingers. 3.A transfer switch structure as specified in claim 2 wherein a. saidcylindrical contact support is provided with a pair of cutouts; b. acontact finger support is inserted into each of said pair of cut-outsand affixed to said cylindrical contact support; c. each of said pair ofcontact fingers is provided with a pair of abutment surfaces eachcooperating with abutment means on said contact finger support to limitthe displacement of said pair of contact fingers under the action ofsaid pair of helical compression springs; and wherein d. said pair ofhelical compression springs is supported by said contact finger supportand tends to cause engagement under pressure of said pair of abutmentsurfaces of each of said pair of contact fingers with said abutmentmeans on said contact finger support.
 4. A transfer switch structure asspecified in claim 3 wherein a. said contact finger support in each ofsaid pair of cut-outs of said cylindrical contact support is bolted tosaid cylindrical contact support and provided with a relatively largecentral passageway and with a pair of additional relatively smallpassageways each arranged to opposite sides of said central passageway,said central passageway and said pair of additional passagewaysextending from one side to the other side of said contact finger supportin each of said pair of cut-outs of said cylindrical contact support; b.each of said pair of contact fingers projects substantially transverselythrough said central passageway of said contact finger support in eachof said pair of cut-outs of said cylindrical contact support; c. each ofsaid pair of helical compression springs is arranged in one of said pairof additional passageways of said contact finger support in each of saidcut-outs of said cylindrical contact support; and wherein d. saidabutment means on said contact finger support in each of said cut-outsof said cylindrical contact support is formed by four pins arrangedsubstantially at right angles to the planes defined by said pair ofcontact fingers.
 5. A transfer switch structure as specified in claim 1wherein a. said cylindrical contact support is provided with a pair ofcut-outs; b. a contact finger support is inserted into each of said pairof cut-outs and affixed to said cylindrical contact support; and whereinc. said contact finger support in each of said pair cut-outs of saidcylindrical contact support supports a stack composed of substantiallyflat finger contacts arranged in parallel planes and including aplurality of pairs of finger contacts, each of said pairs of fingercontacts comprising a pair of spring-biased superimposed contact fingersarranged crosswise to form an X-like pattern.